1. Field of the Invention
The present invention relates to valves and operating mechanisms for operating the valves. Some embodiments relate to a device for providing pressure containment operation of the valve.
2. Description of Related Art
Valves are used extensively in many piping systems such as, but not limited to, transmission pipelines, subsea pipelines, process piping, refineries, and power generation systems. For example, valves may be used with fittings such as the wye fittings disclosed in U.S. patent application Ser. No. 11/796,122 entitled “Reverse Flow Wye Connector” and U.S. patent application Ser. No. 11/857,972 entitled “Pipeline Systems Using A Reverse Flow Wye Connector”, which are incorporated by reference as if fully set forth herein.
A majority of valves include an actuator stem that extends from the blocking element (e.g., a ball, clapper, diverter, gate, or plunger) in the pressurized (e.g., product pressurized) internal cavity to the outside environment. The actuator stem may be sealed by a variety of methods including braid and impregnated packing, elastomer seals, polymer seals, and other types of seals in various shapes and forms. Shapes and forms include, but are not limited to, chevron, o-ring, and lip shapes. The seals contain internal product and pressure by bridging the gap between the valve body and the stem while allowing the stem to rotate relative to the body to actuate the blocking element.
Metal-type seals may be preferred for stem sealing but dynamic (e.g., rotating) metal seals are temperamental and require fine surface finishes and contaminant free environments to operate properly. Over prolonged use and/or over protracted static periods, elastomeric or polymeric valve seals may begin to leak because of deterioration due to product exposure or loss of elastomeric or polymeric properties. Leaking product may create environmental issues, health issues, and/or hazardous conditions in certain systems (e.g., pipeline systems).
In some cases, locking of the stem against inadvertent rotation is desirable to inhibit full or partial closure of the blocking element in certain situations. For example, the stem may be locked to inhibit accidental closure of the blocking element while product is flowing through the valve. Also, for safety, the stem may be locked to prevent accidental opening of the blocking element while personnel are working elsewhere on the piping system.
To solve or avoid some of the problems associated with dynamic metal seals and elastomeric or polymeric seals, a metal-sealed, locking, cap-type device is proposed. The device provides long term pressure containment to seal the stem during static periods when stem rotation is not required. The device also provides locking of the stem against inadvertent rotation.